Heaps

Special lib

Create heap

const {
  MaxPriorityQueue,
  MinPriorityQueue,
} = require("@datastructures-js/priority-queue");
const maxHeap = new MaxPriorityQueue({ priority: (x) => x });
const minHeap = new MinPriorityQueue({ priority: (x) => x });

enqueue(element) - add

maxHeap.enqueue(10);
minHeap.enqueue(5);

dequeue() - delete

let maxElement = maxHeap.dequeue().element;
let minElement = minHeap.dequeue().element;

front() - show top of the heap

let frontMaxElement = maxHeap.front().element;
let frontMinElement = minHeap.front().element;

size()

let sizeMaxHeap = maxHeap.size();
let sizeMinHeap = minHeap.size();

isEmpty()

let isMaxHeapEmpty = maxHeap.isEmpty();
let isMinHeapEmpty = minHeap.isEmpty();

clear()

maxHeap.clear();
minHeap.clear();

toArray()

let maxHeapArray = maxHeap.toArray();
let minHeapArray = minHeap.toArray();

Find top k elements with heap

const { MinPriorityQueue } = require("@datastructures-js/priority-queue");

function fn(arr, k) {
  // Create a min-heap with a custom priority function
  const heap = new MinPriorityQueue({ priority: (x) => x });

  // Iterate over each number in the array
  for (const num of arr) {
    // Add the number to the heap
    heap.enqueue(num);
    // If the heap size exceeds k, remove the smallest element
    if (heap.size() > k) {
      heap.dequeue();
    }
  }

  // Prepare the result array
  const ans = new Array(k);
  // Extract elements from the heap to get the k largest elements
  for (let i = 0; i < k; i++) {
    ans[i] = heap.dequeue().element;
  }

  // Return the result array
  return ans;
}